Urinalysis is a source of information about the anatomy and function of the kidneys and urinary tract. It provides insights into the status of systemic diseases such as diabetes mellitus. The use of test strips, or dipsticks, for urinalysis is widely accepted for health screening purposes because it provides a simple protocol and is very cost-effective.
Dipstick urinalysis is convenient, but false-positive and false-negative results can occur due to the discrimination of color change when it is performed by a human eye, such as by a nurse.
Chronic Kidney Disease (CKD) can be diagnosed in its early stages by a microalbuminuria measurement. The “golden standard” for quantitative measurement of microalbuminuria is from a 24-hour urine collection, but this is very time-consuming and troublesome for patients. Instead, a random spot urine test is most commonly used to screen microalbuminuria, which requires measuring the urine albumin creatinine ratio (ACR), using creatinine to compensate for variations in urine concentration in urine samples.
ACR is also a useful parameter to measure for use as a prognosis factor for kidney failure risk. Monitoring the ACR value during treatment is also useful, and a point-of-care device is required to improve patients' Quality of Life (QOL).
Currently, most of the point-of-care devices available in the market for urinalysis are semi-quantitative and use a test strip and strip reader. A quantitative point-of-care device is desired for home or clinical use.
For example, quantitative urinalysis results can be obtained by using an automatic urine analyzer at the hospital and in a clinical laboratory. A urine analyzer is generally a desk-top machine or part of a larger piece of equipment, such as a fully automated blood serum/urine analyzer. Therefore, the accessibility of these quantitative urinalysis units is centralized and people who live in rural areas have limited access to proper diagnostic tests.
Urine samples have a large pH variation, and the measurement results are also affected by the temperature of the surroundings (i.e. the testing place). Current quantitative assay methods require sample dilution to remove the interference caused by urine. In addition, colorimetric wet reagents for urinalysis are required to be kept in refrigerator, which is not suitable for home or clinical use.
As indicated above, to minimise the effect of pH or interference in current quantitative systems, a urine sample is diluted with a volume of buffer in addition to a strong acid or a strong alkali. To minimise the effect of temperature in the testing room, a cooling system is introduced into the device used for analysis, but this cooling system makes the device bulky. The size of the resulting device makes it difficult to transport and renders it unusable in anything other than a clinical laboratory setting.
In addition, the reagents used in urinalysis may suffer from bubble formation, either occurring during the reaction, or from the addition of the sample to the reagent. This can result in the loss of accuracy due to light scattering.
For current quantitative devices, an internal reference table is normally prepared under a range of pH and/or temperature conditions, so as to normalize the data, but it is troublesome to prepare the reference table and there is a limit on how far the normalisation can be taken, depending on the type of interference. Given this, the result is not accurate for all patients.
As will be appreciated, these problems arise, at least in part, because of the reagents used in the currently available tests.
Given the above, there remains a need for more accurate urinalysis equipment that is portable and which is cost-effective. In addition, there remains a need for analytical reagents that are capable of being tailored for use with a simplified device and which help to increase the accuracy of the result.